Electric discharge lamp



Dec. 27, 1960 J. M. HARRIS ET AL 2,966,605

ELECTRIC DISCHARGE LAMP Filed March 13, 1956 Z6 2a 2a I I I -Zfl /0 5\ 36 i-I #34 /5 1 3y I40 l 30 T\ H II INVENTORS: m/m H 50mm Jmmv M HARRIS BY MARTHA THp/ms United States Patent ELECTRIC DISCHARGE LAMP Joseph M. Harris, Peabody, Keith H. Butler, Marblehead, and Martha J. Thomas, Brookline, Mass., assignors, by mesne assignments, to Sylvania Electric Products, Inc., Wilmington, Del., a corporation of Delaware Filed Mar. 13, 1956, Ser. No. 571,171

1 Claim. (Cl. 313-109) This invention relates to high pressure mercury vapor lamps, and particularly to such lamps having a coating of fluorescent phosphor to enhance the light emission or correct the emission to a desired color.

The invention is particularly related to high pressure mercury vapor lamps in which the light emitted is either blue, blue green, green yellow, orange, or red with a high degree of saturation and in which a considerable part of the light comes from the fluorescence of a phosphor coating on the inner surface of the lamp jacket and in which the color is modified by the use of filters with the filter being an integral part of the outer jacket.

The high pressure mercury vapor lamp (HPMV lamp) consists of a quartz arc tube and an outer protective jacket of glass of considerably larger size, which is generally 30 bluish white in color and is due to intense lines in the are made of clear glass. The light emitted by the lamp is spectrum. at 436, 546. and 578- millim-icrons with weaker lines at 408 and 492 millimicrons, however,- from the standpoint of lumens produced, only the green (546) and yellow .(578) lines are of any importance. Because of this characteristic it is difiicult to change the color of the emitted light either by external filters or by the use of colored glasses for the outer jacket or by the use of filter coats on the outer jacket. In fact the only change that can be made without severe loss of light output is that obtained by using a yellow green filter with substantially no transmission below 500 millimicrons and with high transmission above 530 millimicrons. While it is thus possible to obtain greenish yellow light from the HPMV lamp by the use of a filter, the efliciency is somewhat decreased by the filter and in addition the light lacks a red component so that many colors are distorted. If this filtered yellow-green light is used for street illumination, one particular hazard results in that the red of emergency vehicles appears to be nearly black and cannot be quickly distinguished.

We have discovered that the use of a phosphor coating on the inner surface of the lamp jacket, with said phosphor being preferably selected from one of the compositions described in the copending applications filed on or about March 2, 1956 by Martha J. Thomas and Keith H. Butler, considerably increases the light in all parts of the spectrum and therefore makes it possible to obtain blue, blue green, green, yellow, orange or red light with a high degree of saturation and with relatively high efficency by filtering the light emitted by the fluorescent HPMV lamp through an appropriate filter. While an external filter incorporated in the lamp fixture could be used we prefer to make the filter an integral part of the lamp either by using a colored glass bulb for the outer jacket or by applying a ceramic glaze, colored with a suitable pigment, to the outside surface of the outer jacket prior to coating the inner surface with phosphor.

The use of high efliciency sources of colored light has not been uncommon in street lighting since the introduction of the sodium vapor lamp. However, with the advent may exist.

By using the HPMV lamp with a phosphor applied to the inside of the outer jacket in combination with a yellow filter or with a filter coat on the jacket or with a yellow glass bulb it is possible to obtain a lamp not only distinctive in color but having a lumen output superior I from the phosphor coated lamp, such as the use of: a yellow glass refractor in the luminaire; a yellow glass outer we prefer to use this way of obtaining a colored lamp.

envelop for the mercury vapor lamp; an outer envelop to which a yellow stain has been applied after the bulb has been blown from clear glass; an outer envelop to which a ceramic glaze, consisting of a mixture .of a low melting glass and a yellow pigment, has been applied afterthe bulb has been blown from clear glass; an outer envelop towhich a glaze of a low melting transparent colored glass has been applied after the bulb has been blown from I clear glass.

Other objects, advantages and features of the invention will be apparent from the following specification, taken in connection with the accompanying drawing, which shows a lamp according to one embodiment of the invention.

Referring now to the drawing, the lamp shown therein comprises a fluorescent phosphor coating 1 on the inside surface of an outer jacket or envelope 2 of light-transmitting material within which an arc tube 4 is supported. The are tube 4 is provided with main electrodes 6 and 8 at the ends thereof and an auxiliary electrode 10 disposed adjacent to the main electrode 8. The tube 4 is also provided with a filling of mercury and an inert gas.

A ceramic filter coating 9 is fused to the outside of the jacket 2, in this embodiment of the invention.

The stem press 12 of the outer envelope 2 is provided with a pair of lead-wires 14 and 16, through which the arc tube 4 may be connected to a source of electrical energy. Lead-wire 14, is connected to electrode 8 of the arc tube 4 by a metal ribbon 18. A substantially U-shaped support wire 20 is mounted on lead-wire 16. Collars 22 and 24, which encircle the arc tube 4 adjacent to the constricted ends thereof, are fixedly attached to the legs of the U-shaped wire 20 and thus support the arc tube within the outer envelope 2. A plate 26 bridges the free ends of the U-shaped support wire 20 and is fixedly attached thereto to impart rigidity to the structure. The free ends of the U-shaped support wire 20 are also provided with a pair of resilient metal fingers 28 which are fixedly attached thereto, the ends of the fingers 28 frictionally engaging the inner wall of the constricted upper end of the envelope 2 to further support the structure. Similarly, the lower portion of the legs of the U-shaped support wire 20 is provided with resilient metal fingers 30 and 32 which are fixedly attached thereto, the ends of the fingers 30 and 32 frictionally engaging the inner wall of the constricted lower end of the envelope 2.

Inside the lower end of said envelope 2, a resistor 34 is disposed on wire 20 and is seated on an insulator button 35 which, in turn, rests on the upper longitudinal edge of resilient metal finger 32. Lead-wire 36 of resistor 34 is wound around support wire 20 and it is also welded thereto. This mode of connection has been found to be particularly advantageous because, even if a weld failure should occur, the tight winding of lead-wire 36 about support wire 20 has been found to be adequate enough to maintain the electrical circuit through these members. Lead-wire 38 of resistor 34 is welded to metal ribbon 40 which is in turn connected to auxiliary electrode 10 of the arc tube 4.

Although considerable rigidity is imparted to the structure by positioning the resistor 34 on support wire 20 and winding lead-wire 36 of resistor 34 about support wire 20 and welding it thereto, additional structural rigidity may be obtained by positioning the resistor 34 on the support wire 20 so that the lower end thereof is seated on insulator button 35 and the upper end thereof is engaged by a depending flange 42 of collar 24. Another advantage which accrues from the use of insulator button 35 is the elimination of arcing, since the button 35 prevents contact between the body of resistor 34 and support wire 20; this displacement prevents electrolysis and ultimate arcing through the resistor core.

Specific examples of phosphor coatings I and ceramic filter coatings 2 are given below, but we do not wish to belimited thereto.

Example I The bulb used for the outer envelop of a 100 watt HPMV lamp was sprayed on the outer surface with a mixture composed of 90 parts of a low melting glass and 10 parts of cadmium sulfide and then heated to a temperature high enough to fuse the low melting glass thus forming a yellow ceramic glaze on the bulb. The inner surface of this yellow bulb was then coated with a phosphor whose mole composition was 2.65 SrO, 0.20 2110, 1.00 P 0.06 SnO. The bulb was then made into a HPMV lamp by sealing in a quartz arc tube. Calculation of the color coordinates on the CIE diagram, from the measured spectral energy distribution gave x=.415, y=.561. This corresponds to a dominant wavelength of 567 millimicrons with a saturation of 94%. The lumen output was 2500 lumens while the same type of arc in a clear bulb gave 3000 lumens. Thus a good yellow light of high efiiciency was produced.

Example [I The bulb used for the outer envelop of a 400 watt HPMV lamp was stained by spray coating with a paste containing copper sulfide, iron sulfide and clay, firing to allow the copper and iron to enter the glass, and then removing the excess paste leaving the bulb stained a greenish yellow. The inner surface of the stained bulb was coated with the phosphor of Example I and made into a lamp. The emitted light was a good yellow and the lumen output was 19,000 lumens. A similar lamp with clear glass was found to have an output of 21,000 lumens.

While HPMV lamps combining the phosphor coat with the use of a yellow filter are outstanding in their performance it is also possible to modify the color of the light by other filter colors such as blue, blue green, green, orange or red and to obtain colored light with a higher degree of saturation at much higher efiiciency than it is possible to obtain with incandescent lamps in combination with filters.

Example III The bulb used for the outer envelop of a 100 watt HPMV lamp was sprayed on the outer surface with a mixture of parts of a low melting glass and 5 parts of a cobalt blue pigment and then heated to fuse the ceramic glaze on the bulb. The inner surface was then coated with a phosphor whose composition was 2.05 CaO, 0.80 ZnO, 1.00 P 0 and 0.04 SnO. This bulb was then made into a lamp. It was found to give an intense blue light much stronger than that of a 250 watt incandescent lamp with a blue filter.

Similar results were obtained when green, orange or red filter coats were applied to the bulbs or when a colored glass was employed for making the bulbs. In making these lamps the composition of the phosphor is varied so that the maximum output of light of the desired color is obtained.

In addition to the use of these colored lamps for cautionary use in street and highway lighting they can also be used for color flood lighting where high intensity is desired.

An example of a low-melting pointglass is one of the following composition:

The foregoing example is given merely by way of illustration and not by way of limitation, as various other compositions can be used.

Various modifications and embodiments of the invention will be apparent to a person skilled in the art, without departing from the spirit and scope of the invention.

What we claim is:

A high pressure mercury lamp comprising an inner arc tube, an enclosing light-transmitting outer jacket, 2. coating of phosphor on said jacket, said phosphor emitting yellow light and other colors of light, and a yellow ceramic glaze on said jacket to transmit the yellow light and absorb the light of shorter wavelengths, said phosphor having a mole composition of 2.65 SrO, 0.20 ZnO, 1.00 P 0 0.06 SnO.

References Cited in the file of this patent UNITED STATES PATENTS 1,765,242 Reiter June 17, 1930 2,177,705 Friederich Oct. 31, 1939 2,177,755 Uyterhoeven Oct. 31, 1939 2,211,590 Addink Aug. 13, 1940 2,290,186 Holman et a1 July 21, 1942 2,723,958 Shaffer et al Nov. 15, 1955 

